Duplex telegraphy



@m M; HQMO 1 5111326 J. M. FELL DUPLEX TELEGRAPHY Filed Nov 16 1921 INVENTOR QZMZFMZ Patented Get. 14, i924.

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JOHN M. FELL, F HAGKENSACK, NEW JERSEY, ASSIGNOB T0 AMEBIGAN TMI JEEQNE AND TELEGRAPH. GOM'PANY, A COEPORATIQN OF NEW YORK.

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Application filed November To all whpm itmay camera; I a

Be it known that I, JOHN M. FELL, resid ing at Hackensack in the county of Bergen and State of New ersey have invented certain Improvements in IluplexTelegraphy,

of which the following is a specification.

This invention relates to duplex telegraph systems and particularly. to such systems .urtilizin lines operated with a ground return. 'le the arrangements of the invention may be utilized for full duplex operation, i. e.,-transmission both ways simultaneously, they are particularly applicable for so-called half duplex operation, i. e., 5 transmission one way at a time. One ofthe cardinal featuresot' the invention consists in the utilization of polarized relays and the novel arrangement of such relays and amociated apparatus at the telegraph stations. With such arrangements the transmission and service on duplex telegraph systems may be materially improved.

In half duplei transmission one loop is used for both transmitting and receiving signals. Thepole changer which transmits into the line is'included in this loop. Signals are produced in the loop by opening and closing it. Outgoing signals must operate the pole changer but incoming signals must v not. -To prevent operation of the pole chan r b incomin si als, means are, provide for locking ii i its closed position when the loopisopened by an incoming signal. In former well known arrangements 0 duplex systems for grounded lines, incoming signals operate a polarized line relay and this, in turn, operates a local circuit relay called a control relay which repeats the signals into the loop circuit and, at the same time, by means of a supplementary contact, actuates a locking winding on the pole changer when the loop is opened by a space signal. The control relay and pole changer are both neutral type relays and, consequently, the eficiency of such systems is somewhat limited.

Another requirement of half duplex operation is to provide means for breaking, i. 'e, getting control of the circuit from a loop while incoming signals are being repeated into the loop. A break can always be started when the contact which repeats incoming signals into the loop is closed, butts insure complete transmission the repeatpole changer locking contnctsmust 18, i921. Serial No. 515,643.

be made inoperative as soon as the break is initiated. In former well known arrangements of duplex systems this was accomplished by causing a sounder, which is released by a break signal, to close a circuit through the control rela causing it to keep the repeating contact 0 osed and the pole changer locking circuit ino rative. To establish this condition the po e changer armature must first move a "sufiicient distance to open the sounder circuit; then the sounder armature must move from its front to its back contact. This relayis undesirable and 'reduce s'theefiiciency of the break feature in former types of systems.

In the arrangements of this invention polarized relays are usedas pole changer, control and .break relays, instead of the neutral pole changer and control relays and neutral sounder of the formersystems hereto-.

fore referred to. Thereceiving relay is also 1 polarized as in former arrangements. The pole changer-and break relays each have two windings. One winding of each relay,

' referred to as the marking winding, is connected in series in the local loop' circuit and when current flows in this circuit the armatures of both relays are moved to their marking contacts. The other winding of each re lay, referred to as the spacing winding, is 85 in a local battery circuit normally kept closed. The current in these windings is limited to about one half of that in the marking windings and this current-tends to pull the armatures toward their spacin 99 contacts. \When the loop circuit is close I the greater current in the marking windings keeps the armatures on their marking contacts, but when the loop circuit is opened,

1 except at the receiving relay, current in the 95 spacing windings instantly moves the armatures to their spacing contacts. The receiv-e ing relay and the control relay are operated simultaneously by incoming signals. Each time the receiving relay opens the loop circuit, the control relay causes a reversal of current in the spacing windings of pole changer and break relays, thus converting them temporarily to holding windings which keep the armatures on. their marking con tests. This prevents a transmission oi" in coming signals back to the line circuit. v

The break relay operates simultaneously 'with the pole changer. -Vi "hen its: geared to the sp-aeing'contact, spacing battery is directly connected to the pole changer and break relay spacing windings. This makes the transmission of a break signal, once it is started, independent of the action ofthe receiving and control relays. The only time required to establish this condition is the armature travel time of the polarized break relay. This time is less than that required for the break operation as pointed out for former types of duplex systems and accordingly the efficiency of the break operation is increased.

The arrangements of the invention serve to materially improve the service on duplex v telegraph systems. A few features of such improvement may be-specifica-lly cnumerated as,a reduction of the number of repetitions over former systems by repeating directly from the line to the loop; improved transmission by utilizing polarized instead of neutralrelays; an improvement in the break feature by reducing. the time required' to establish it. Furthermore the relay arrangements of the invention are such as to permit the combination of two or more I sets to make a repeater for, joining two or more lines in one'circuit, operable fromany station in it.

The invention may bemore fully understood from the following description when read in connection with the accompanying drawing. In Fig. 1 of the drawing the ar- Ii rangementsof the invention are illustrated in a circuit arranged for half duplextrans mission between two stations. In Fig. 2 the duplex sets of the invention are shown as pepeaters for interconnecting a plurality of mes.

In Fig. 1 of the drawing are shown two terminal stations X and Y joined by a line L and the equipment at each station when the system. is used 'for half duplex operation. The duplex set at'station X has four polar relays 1, 2, 3 and 4, each relay having two windings arranged differentially. Relays 3 and 4 are connected differentially in the line and artificial .line circuits, L and AL respectively, in a manner well known in the art, and are operated by signals arriving from station Y but ,are non-responsive to signals originating at station X. Relays 1 and 2 each have one winding, a and c, in

the'local receiying circuit. This circuit insecond windings of relays 1 and 2, band drespectively, are in series in a local circuit.

eludes battery B, key K, windings a and 0, contact 14; ofrelay 4, sounder S,-, and a loop circuit which 11* ,y extend to a substation andinclude key K, and. sounder S This loop circuit, however, may be omitted and the sounder S, may be grounded. The

as follows,from ground, through windlngs b and d, thence through parallel paths, one ofwliich includes resistance r and bat- "tions.

tery 13,, while the other path includes resistance 1", and battery-13,. The: potential of, or the resistances in series with, the bat-' and (i (then due to batteryB is reversed and produces the same efiect n relays 1 and 2 as the normal current in windings a and c. The relay 4 may be termed the line relay, relay 3 the control relay, rela 2 the break relay, and relay 1 the pole c anger.

Relay 4 controls contacts 14 and 14:, relay 3 controls contacts 13 and 13 relay 2 controls parts beingrepresented with like reference. characters with primeindices added.

The operation of-these arrangements is as follows The relays and keys are represented in the drawing in their normally closed posi- If now the key K or K, at Y is opened to produce a sgace signal the spacing impulse arriving at moves the armatures of relays 3 and 4 from; contacts 13 and 14 to contacts 13 and 14 respectively. When contact 14 opens, current ceases to flow in windings a and c of relays 1 and 2 and in sounders S, and S Sounders S, and S open but since contact 13 of relay 3 opens simultaneously with contact 1 1 of relay 4 battery B, is disconnected and current from battery B flows through the windings b and d of relays '1 and 2 in a direction to keep contacts 11 and 12 closed; thus relays 1 and 2 do not operate and relay 1 does not repeat the incoming signal back to station Y. Closing the key at station Y causes a marking impulse to be transmitted to station X,

which moves the armatures of relays 3 and' 4 to contacts 13 and 14; respectively and thus restores the apparatus to the condition as shown in the drawing.

Opening key K at station X to transmit a spacing signal stops the flow of current contacts 12 and 12 and relay 1 controls through windings a and 0 of relays 1 and 2 and through sounders S, and S As'contact 13 b-f relay 3'is closed current from battery B,- fiows' through the windings b and d of relays land 2 ina direction to move their armatures from contacts 11 and 12to contacts 11 and 12 respectively as p soon as current ceases toflow in windings a and c. When contact 11 closes, current from spacing battery 13, ows to line L through windings e and g and to artificial line: AL througn windings f and h of relays 3 ands. fllhis reversal of current through both w ndings of relays 3 and 4:, as the windings are differentially arranged, producesno operative efiect in them, but the;

battery to Winding b and d and consereversal of the current in the line L operates the line relays 3'and4 at station Ya When contact'1-2 of relay 2 closes, anew circuit is provided from battery B, to windings b and d of relays l and 2 which is in parallel with the circuit'through contact 13 of relay 3. The purpose of this circuit will be described hereinafter in connection with the break feature of the system.

Sounders S, and .S, are released when key K or K, is opened. The polarized sounder S, which is connected in a leak circuit from .the armature of the pole changer relay 1, is also released when the line bat tery is reversed. Sounders S and S indicate to the terminal station and substation attendants respectively the signals produced in the loop circuit and sounder S indicates to the terminal station .attendant that signals originating in the loop circuit are properly transmitted to line L.

' When key K or K is again closed relays -1 and 2 and sounders S and S are restored to their normally closed conditions and when contact. 11 of relay 1 closes, sounder -S closes, and a marking im ulse is transmitted which restores the instruments at station Y to' their normally closed positions. i

It will be; seen that when the sets are used with four relays in the above described manner that signals can be transmitted one way at a time only, for when key K'or K is open no signal can be produced in the re-v ceiving circuit by the operation of relay 4, and when the contacts of relays 3 and 4 are open relays 1 and 2 can not be operated I liver.

by key K or K In sin is transmission systems it is es sential t at anoperator at a receiving station shall have means for breaking the operator who is sending in order that the breaking operator may himself transmit when he has an important n essage to de For efiicient telegraph service the breaking means must be quick and re- I liable. In the arrangements of this in 'vention an' eficient breaking means is pro' vided through the agency of the relay 2;

i As has been heretofore described relays 1 and 2 are kept closed when signals are being j received, for when relays 3 ands. are closed the greater current in windings a and 0 hold relays 1 and 2 closed and when relays 3 and 4: are open the currentfrom battery flows through windings band d in a direction to keep them closed. if key K or K, is opened to break while relays 3 and dare closed current ceases to flow in windings a and 0 of relays 1 and 2, thereupcn,.current in windings b and a? from batand 12 to contacts 11 and 12 respective- Contact 12 closes the circuit irrora battery B,- forming a new path from that qu'ently relays 1' and 2 will still receive spacing current from battery BI, even t ough contact 13 of relay 3 should again be opened by an incoming spacing signal. Since these relays are now under control of the open key (K or K), a space signal is sent to stat-ion Y frombattery B over ey is opened to transmit a break signal whlle relays 3 and 4 are open. In this case v the break is delayed until contact 13 of relay 3 is closed. When this contact closes current from battery B through windings b and (3 opens relays 1 and 2 (although contact -14 closes Simultaneously no current flows in windings it and 0 because of the open key) and then contact 12 provides a new path for battery lit and places relays 1 and 2 (and the transmission of, the break signal) under control of the open key even though relays 3 and 4 may again open.

In Fig.2 are shown a plurality of the duplex sets of this invention, such as A and B, utilized to connect a plurality of lines such as L, and "L into one operating circuit for single transmission. Like reference characters have been used to denote like parts with respect to Fig. 1. In this arrangement the line relays, such as 3 and 4 and 3- and a", are connected with their respective line circuits L and L The windings a and c of the relays such as 1 and 2 and 1 and 2" are connected, as shown, in series in a local loop circuit. This circuit may be terminated by ground at conductor tion of the arrangements would be substantially the same as heretofore described with respect to Fig. 1 no further description thereof will be given.

circuit and thence into each While the invention has been illustrated inf certain specific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many other and widely varied forms without departing from the spirit of the invention as defined in the appended-claims.

lVhat is claimed is:

l. A duplex telegraph set comprising a loop circuit, a polarized pole changer, re-l lay and a polarized break relay having windings serially included in said loop Circuit and additional windings on said relays, a circuit the potential'o'l which is normally opposite to that of said loop circuit, said ad ditional windings being included in said circuit.

2. Aduplextelegraph set comprising a receiving relay and a control relay, a loop circuit, a polarized pole changer relayand a polarized break -relay having windings included in said loop circuit, additional windings on said two last mentioned relays, said additional windings being included in a circuit the potential of which is normally opposite to that of said .loop circuit,. and means controlled by said receiving relay and said control relay for opening said loop circuitand reversing the potential in the other circuit.

3. Aduplex telegraph set comprising a receiving relay and a control relay, a loopcircuit, a cpolarized pole changer relay having a Win ing serially included in said loop circuit, a source of current in said loop circuit of a polarity such that when said loop circuit is closed the contacts of said relay .will be maintained in a predetermined position, a second winding on saidpolarized relay, said winding being lncluded in a local circult, a second source of current associated with said local circuit of a polarity tending to reverse the predetermined position of said relay contacts, a third source of current associated with said local circuit of a polarity tending to i'naintainisa'id relay contacts in said predetermined position, the

potentialof said first mentioned source 9f current being greater than the potential of said second source and the potential of said second source being greater than said third source, and means whereby said receiving relay may control said loop circuit and whereby said control relay may control said local circuit.

r 4. A duplex telegraph set comprising a receiving relay and a control relay, a loop circuit, a polarized po'le changer relay and a polarized break relay having windings in-' cluded in said .loop circuit, additional windings on said two last mentioned relays, said additional windings being included ,in a local circuit the potential of November 1.921,

. JOHN M. FELL. 

